Remark 3.2 
As in [1]}, we may also consider the case where the system has more than two blocs. More precisely, consider a bloc triangular system \([A]\) , where
\(A=\left(\begin{array}{cccc}A_1 & A_{1,2}&\dots &\\& A_2 & A_{2,3}\\&&\ddots & \\0&&&A_k\end{array}\right).\) 
